Motors for use in electrical equipment mounted in automobiles, for example, are required to have high reliability as well as compact size and reduced weight.
One of the motors of this type is a commutator motor which has brushes and a commutator. The commutator motor generally includes a stator which forms a magnetic field and a rotor which is disposed to face the stator via an annular gap. The rotor is equipped with a so-called armature including the commutator. The armature is supplied with electric power to rotationally drive the commutator motor. Moreover, to supply the power to the armature, brushes are disposed which are connected to an external direct current power supply. Such the brushes are in contact with the commutator to supply the power to the armature. Moreover, the rotor includes the commutator that is configured with a plurality of commutator pieces (segments) disposed in an annular or cylinder shape, as well as an iron core on which windings are wound. Furthermore, for the commutator, hook-type commutator is commonly used which includes the commutator pieces, each having a hook to connect the windings. Following a predetermined method of connecting wires, the armature is formed in such a way that the windings are wound on the iron core, with the windings being connected to the hooks by hooking or winding them on the hooks.
In connecting the windings to the hooks in the hook-type commutator, a technique for winding the winding on the hook in an α-shape has been generally used. Here, “winding the winding on the hook in an α-shape” as referred herein means a way of winding the winding on the hook in a letter“α” motion. As an example of such the winding-on-a-hook, a technology has been proposed to provide stable wire spacings when the windings are wound on the hooks in the α-shape (see Patent Literature 1, for example). In the technology, step heights are disposed in hook-root winding parts such that, in each of the hook-root winding parts, the outer peripheral surfaces of the right and left sides are different in height from each other.
Moreover, in the commutator motor, a technology has been proposed which is aimed at improving driving efficiency and reducing its size and weight, by devising a different wire connection structure of the windings (see Patent Literature 2, for example). Next, conventional examples of such the wire connection structure of the windings will be described.
First, in the conventional examples, the armature coil is configured including a plurality of coil units and a plurality of jumper wire units. Here, the coil units are coils wound on teeth. The jumper wire units are wires to interconnect electrically between the coil units. Moreover, in a segment group of the commutator, the segments are divided into three types: a first segment connected with one end of the coil unit, a second segment connected with the other end of the coil unit, and a third segment connected only with the jumper wire unit. The first segment and the second segment are arranged adjacent to each other. Next to this adjacent arrangement, the third segment is arranged. Then, the armature coil is configured including the jumper wire units that pass through slots to interconnect between the coil units.
FIGS. 5A and 5B are views of one example of the wire connection of such the conventional jumper wire units. FIG. 5A is a top view of conventional armature 96 while FIG. 5B is a side-elevational view of armature 96. Note that, in FIGS. 5A and 5B, only one jumper wire unit is exemplified for the sake of brevity.
As shown in FIGS. 5A and 5B, jumper wire unit C91, which comes from first segment S2 disposed on the upper surface of armature core 17, passes through slot SL12 between coil unit W1 and coil unit W2 to reach the lower surface side of armature core 17.
Moreover, jumper wire unit C91 passes under the lower surface side of coil unit W2, and passes through slot SL23 between coil unit W2 and coil unit W3 to reach the upper surface side. Then, jumper wire unit C91 is wound on the hook of third segment S10 in an α-shape and is then connected to third segment S10.
Next, jumper wire unit C91 exits from third segment S10, and passes through slot SL34 between coil unit W3 and coil unit W4 to reach the lower surface side of armature core 17.
Furthermore, jumper wire unit C91 passes under the lower surface sides of coil unit W4 and coil unit W5, and passes through slot SL56 between coil unit W5 and coil unit W6 to reach the upper surface side. Then, jumper wire unit C91 is connected to second segment S18.
In this way, the conventional commutator motor is configured including the wire connection in which the jumper wire unit passes through the slots to reach the third segment.
As described in the above conventional example, when the winding is connected to the third segment, the winding of the wire unit on the hook in the α-shape allows ease of the method of connecting the windings and secured connection quality. However, there has been a problem that the wire unit tends to come into in contact with the hooks of the segments adjacent to the third segment, resulting in insufficient wiring quality. In particular, as shown in FIGS. 5A and 5B, the closer diameter Dc of the commutator becomes to inner-peripheral diameter Ds of the slots of the iron core, the more easily such the contact occurs. One example of this is such that, like the route of jumper wire unit C91 from third segment S10 to slot SL34 shown in FIGS. 5A and 5B, jumper wire unit C91 tends to be wired to lie close to the hook of segment S9 and wired to run into below the underside of the hook of segment S9. This results in the tendency for the wire unit to suffer contact at this point. Then, the jumper wire unit part of the winding comes in contact with the hook to cause damage to the winding, resulting in easy occurrence of insulation failures and short circuit failures at the contact point.
Moreover, when such the commutator motor is mounted in an automobile, there has been a possibility that such the contact occurs due also to vibrations because the windings are subjected to vibrations from the automobile in addition to ones from the motor itself.